Ruthenium fabrication



Oct. 22, 1963 R. a. coma:

RUTHENIUM FABRICATION Filed 001;- 17, 1961 \EwiWQ vOiw OW X IO 20Conmcrme P ESSU E /5: 1.

INVENTOR. ,Poaqw- @50 6: COPE Array/vs Unite States atent 3,1t38,000.RUTHENIUM FABRTCATEGN Robert G. Cope, Troon, Ayrshire, Scotland,assignor to The International Nickel Company, Tum, New York,

N.Y., a corporation of Eeiaware Filed Get. 17, 1961, Ser. No. 145,721iaims priority, appiication Great Britain Oct. 24, 1960 3 Claims. (Cl.75-214) The present invention relates to the production of metalarticles and, more particularly, to the production of ruthenium metalarticles.

It is known to produce fabricated platinum by decomposing a platinumsalt to yield platinum powder, pressing the powder into compacts,sintering these compacts and working them to the final form by hot orcold working, or both.

However, when attempts are made to produce fabricated ruthenium by asimilar process, faults generally arise at one or more of the differentstages. The powder produced may not readily compact, the compacts maycrack during sintering and otherwise sound sintered compacts may yetcrack during hot working. Although attempts were made to overcome theforegoing difficulties and other disadvantages, none, as far as I amaware, was entirely successful when carried into practice commerciallyon an industrial scale.

It has now been discovered that by a specially controlled powdermetallurgical process, the drawbacks of the prior art can be avoided andthat dense ruthenium articles can be manufactured.

It is an object of the present invention to provide a novel process forthe production of ruthenium metal articles.

Another object of the invention is to provide a novel process for theproduction of ruthenium metal articles employing commercially availabletechniques.

The invention also contemplates providing novel ruthenium metalarticles.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the accompanying drawing which isa graphic illustration of the relationship among ruthenium particlesize, percentage of theoretical density and compacting pressure ascontemplated in accordance with the present invention.

Generally speaking, the present invention contemplates a novel processcomprising compacting ruthenium powder having a surface area of between2 and 10 square meters per gram (m. gm.) and advantageously between 2and about 5 m. /gm., under a pressure less than about 20 long tons persquare inch (t.s.i.) such that the sintered density will be greater than90% of the theoretical density of solid ruthenium, sintering saidcompact at a temperature in excess of about 1350 C. and advantageouslyin excess of about l400 C. and up to about 1600 C. to form a sinteredcompact having a density greater than about 90% theoretical andthereafter hot working the sintered compact at a temperature in excessof about 1200 C.

If the sintered density is less than 90%, there is a danger that duringsubsequent working, stress concentrations caused by excessive porosity,will be set up and cracking will ensue. With powder having a surfacearea, measured in accordance with the procedure described by P. Herschin the Journal of the Institute of Metals, 1957, volume 86, pages 509 to511, greater than m. gm. there is a danger of cracking during sintering.With powder having a surface area of less than 2 m. /gm., the requireddensity of the sintered compact can be obtained only if very highsintering temperatures are used. These 7 3,108,000 Patented Get. 22,1963 ice powder of low surface area, say 2.0 m. /gm., high pressures, upto 20 t.s.i. are generally required. The relationship among compactingpressure, surface area of the ruthenium powder and percentage oftheoretical density for a sintering temperature of 1450 C. isillustrated by the drawing. Referring now thereto, it is to be notedthat by employing compacting pressures of about 0.5 t.s.i. to about 12t.s.i. in combination with powders having a surface area of about 2.71m. /gm. to about 9.85 m. /gm., compacts having at least abouttheoretical density are obtained after sintering at about 0 C.

The sintered density also depends on the sintering temperature used,increasing as this temperature increases. The compacting pressurerequired will thus thus be lower the higher the sintering temperature.

Powder having the surface area required can be obtained by directlyigniting ammonium ruthenium chloride in hydrogen at temperatures between400 C. and 550 C. If the temperature is below 400 C., powder of surfacearea greater than 10 m. gm. is produced and, if it is above 550 C., thenpowder with a surface area of less than 2 m.'/ gm. is obtained.

The powder can also be produced from other simple compounds such asruthenium chloride and ruthenium dioxide, and from more complexcompounds of ruthenium which, on ignition or reduction, leave either aresidue which can readily be separated from the ruthenium, or no residueother than the ruthenium itself.

The range of temperature to which the ruthenium compound should beheated to obtain ruthenium powder will depend on the particular compoundchosen. As the temperature increases, the surface area decreases andwhatever compound is used, must be heated to a temperature such thatpowder having a surface area of between 2 and 10 m. /gm. is produced.

The sintering can be carried out in a neutral or reducing atmosphere,including a vacuum. Advantageously, the sintering is conducted in avacuum. The temperature of sintering should be above 1350 C., for belowthis temperature the grain structure obtained does not deform in asuitable manner when the sintered product is hot worked. Advantageously,the sintering temperature is below about 1550 C.

When sintering in a vacuum, a suitable sintering temperature is about1500 C., or somewhat higher temperatures if the powder has a low surfacearea within the range according to the invention. If the powder issintered without using a vaccum, cracking occurs more readily during hotworking.

The hot working may be carried out within the same tempreature range asthe sintering. Rolling or swaging can be efiected with conventional rollgap or die sizes.

For the purpose of giving those skilled in the art a betterunderstanding of the invention and/or a better appreciation of theadvantages of the invention, the following illustrative example isgiven:

Example Some ammonium ruthenium chloride was ignited at 525 C. underhydrogen. The surface area of the powder thus produced was 4.86 m. /gm.The powder was then compacted by hydrostatic pressing at 5 t.s.i. The

compact in the form of a rod was sintered in vacuo at 1450 C. at apressure of 0.0001 mm. of mercury for 15 hours. The sintered compacthaving a density of 93% of the theoretical density of solid rutheniumwas hot swaged using a holding furnace temperature of 1450 C. and aprotective hydrogen atmosphere during reheating between swaging passes.There was a 96% reduction in area of the rod, of which the diameter wasreduced from 0.5 inch diameter to 0.1 inch diameter. The fabricated rodwas found, on examination, to be prefectly sound, apart frominconsequential surface cracks of the usual kind.

The present invention is particularly applicable to the production ofrods, wires, sheets, crucibles, tubes, etc.

lthough the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be restored to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. Such modifications and variations are considered to bewithin the purview and scope of the invention and appended claims.

I claim: l. A process for the production of wrought ruthenium metalcomprising compacting ruthenium metal powder having a surface area ofabout 2 to about 10 square meters per gram at a pressure of about 0.5long tons per square inch to about 20 long tons per square inch,sintering said compacted powder at a temperature of about 1350 C. toabout 1600 C. to provide a sintered compact having a density greaterthan about 90% theoretical and thereafter hotworking said sinteredcompact at a temperature in excess of about 1200 C.

2. A process as claimed in claim 1 wherein the ruthenium powder has amaximum surface area of about 5 square meters per gram.

3. A process as claimed in claim 1 wherein the, ruthenium metal powderhas a surface area of about 2.71 to about 9.85 square meters per gram,the meal powder is compacted under a pressure of about 0.5 to about 12long tons per square inch and the sintering is conducted at atemperature of about 1450 C.

OTHER REFERENCES Journal of the Less Common Metals, vol. 1, No. 4,

August 1959, pp. 269-291.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,108,000 October 22, 1963 Robert G. Cope It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 2, line 23, strike out "thus", second occurrence;

line 0 for "tempreature" read temperature column 3, line 10, for"prefectly" read perfectly lines 16 and 17 for "restored" read resortedcolumn 4, line 13, for "meal" read metal Signed and sealed this 28th dayof April 1964,

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. A PROCESS FOR THE PRODUCTION OF WROUGHT RUTHENIUM METAL COMPRISING COMPACTING RUTHENIUM METAL POWDER HAVING A SURFACE AREA OF ABOUT 2 TO ABOUT 10 SQUARE METERS PER GRAM AT A PRESSURE OF ABOUT 0.5 LONG TONS PER SQUARE INCH TO ABOUT 20 LONG TONS PER SQUARE INCH, SINTERING SAID COMPACTED POWDER AT A TEMPERATURE OF ABOUT 1350*C. TO ABOUT 1600*C. TO PROVIDE A SINTERED COMPACT HAVING A DENSITY GREATER THAN ABOUT 90% THEORETICAL AND THEREAFTER HOT WORKING SAID SINTERED COMPACT AT A TEMPERATURE IN EXCESS OF ABOUT 1200*C. 